High flow-low pressure irrigation system

ABSTRACT

A high-flow low-pressure irrigation system ( 10 ) for directing a fluid to and recovering the fluid from an area within a body, the irrigation system ( 10 ) comprising a sheath ( 37 ) and a flexible catheter ( 20 ) disposed in the sheath ( 37 ). The catheter ( 20 ) comprises a plurality of apertures ( 26 ) at a distal pigtail portion ( 28 ). The fluid is directed through the apertures ( 26 ) and recovered through the sheath ( 37 ). Renal applications include alkaline irrigation for dissolution or uric acid stones, chemo-dissolution of cystine stones, irrigation with chemotherapy drugs after ureteroscopic tumor management, antibiotic irrigation for severe infection (e.g. fungal and bacterial), and irrigation of thrombotic agents (Alum Or direct delivery of Amicar for renal bleeding).

This application claims benefit to U.S. Provisional Application Ser. No.60/329,139 filed Oct. 12, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to renal cooling systems and,more particularly, to a high-flow low-pressure irrigation system for usein minimally invasive surgery.

2. Description of Related Art

Complex renal surgery frequently requires transient interruption of therenal vasculature. Renal hypothermia is known in the field to protectthe kidney from ischemia-induced nephron loss and to preserve renalfunction during partial nephrectomy, renovascular surgery and kidneytransplantation. Renal hypothermia is achieved by clamping the renalartery and packing the kidney in ice or slush. Although this practiceprovides sufficient cooling of the kidney, it presents many drawbackssuch as exposing the surrounding structures to the cooling effects ofthe ice or slush and obscuring the surgical field of view by the ice orslush. Moreover, the practice of packing the kidney in ice or slush isnot feasible for minimally invasive or laparoscopic surgery.

With growing interest in laparoscopic surgery, the inability to achieverenal hypothermia during laparoscopic surgery has become a significantproblem. Accordingly, there is a need in the art for a renal coolingsystem for use during minimally invasive surgery and, in particular, ahigh-flow low-pressure irrigation system.

SUMMARY OF THE INVENTION

The present invention is directed to a high-flow low-pressure irrigationsystem for directing a fluid to and recovering the fluid from an areawithin a body. The irrigation system comprises a sheath defining asheath lumen and a flexible catheter disposed in and through the sheathlumen. The flexible catheter defines a catheter lumen and comprises aplurality of apertures at a distal portion that extends beyond thesheath lumen and spreads in the body area. The fluid is directed andoutputted to the body area through the catheter lumen and the apertures,and the outputted fluid is recovered and returned through the sheathlumen. The irrigation system can be endoscopically placed inside a bodycavity such as the kidney prior to laparoscopic surgery. The fluid maybe a cooling solution such as saline, which is introduced to theirrigation system to allow for preservation of renal tissue during renalartery clamping. A feature of the invention is that only the lumen beingirrigated, the catheter lumen, is exposed to the fluid or coolingsolution. An advantage of the system of the invention is the fluid orcooling solution can be delivered directly to a very defined space viathe catheter lumen while the pressure is kept low by the sheathrecovering the outputted fluid. In a renal application, for example, thecatheter lumen can deliver the cooling solution directly to thecollecting system of the kidney as the access sheath tamponades theureter and the bladder is completely bypassed. Another feature of theinvention is it can be made as a one-piece system that can be easilydeployed.

Renal applications of the system include alkaline irrigation fordissolution of uric acid stones, chemo-dissolution of cystine stones,irrigation with chemotherapy drugs after ureteroscopic tumor management,antibiotic irrigation of intra-abdominal abscess and severe infection(e.g., fungal and bacterial), and irrigation of thrombotic agents (Alumor direct delivery of Amicar for renal bleeding).

DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included in and constitute a partof this specification, illustrate the embodiments of the invention and,together with the description, explain the features, advantages andprinciples of the invention. In the drawings:

FIG. 1 illustrates a high-flow low-pressure irrigation system inaccordance with a first embodiment of the invention;

FIG. 2 illustrates a flexible catheter of the irrigation system of theinvention;

FIG. 3 illustrates an exemplary access sheath for use in the irrigationsystem;

FIG. 4 illustrates the flow of entering fluid and returning fluid in theirrigation system;

FIG. 5 illustrates the irrigation system flushing out stonefragmentations from a body cavity;

FIG. 6 illustrates a high-flow low-pressure irrigation system inaccordance with a second embodiment of the invention;

FIG. 7 illustrates a high-flow low-pressure irrigation system inaccordance with a third embodiment of the invention;

FIG. 8 illustrates a high-flow low-pressure irrigation system inaccordance with a fourth embodiment of the invention;

FIG. 9 illustrates another embodiment of the flexible catheter of theirrigation system;

FIG. 10 illustrates yet another embodiment of the flexible catheter ofthe irrigation system;

FIG. 11 illustrates a high-flow low-pressure irrigation system having anintegrated catheter and access sheath in accordance with anotherembodiment of the invention; and

FIG. 12 illustrates a cross-sectional view of the integrated catheterand access sheath of the irrigation system of FIG. 11.

DESCRIPTION OF PREFERRED EMBODIMENTS AND BEST MODE OF THE INVENTION

FIG. 1 illustrates a high-flow low-pressure irrigation system 10 inaccordance with a first embodiment of the invention. System 10 comprisesan access sheath 37 and a flexible ureteral catheter 20 disposed insidesheath 37. Sheath 37 includes a sheath outer surface 40 and a sheathinner surface 41 as best illustrated in FIG. 4. Referring back to FIG.1, a sheath funnel 42 is disposed at a sheath proximal end 38 andincludes a sheath proximal opening 44. A sheath tube 46 extends distallyfrom sheath funnel 42 to a sheath distal end 39 where a sheath distalopening 48 is disposed. Sheath tube 46 defines a sheath lumen 49. It ispreferable that the length of sheath 37 is less than the length ofcatheter 20 such that catheter 20 extends through sheath 37 andprotrudes out of sheath distal opening 48. In particular, when extendedthrough sheath 37, a distal tube portion 28 of catheter 20 is notenclosed within sheath 37. Referring to FIG. 2, catheter 20 ispreferably curled resembling a pigtail at distal portion 28 and maycomprise a catheter connector 22 at a proximal end 24. It should benoted that distal portion 28 of catheter 20 may have differentconfigurations to provide optimal irrigation, for example, distalportion 28 may be flared to provide a wide dispersal of irrigant orangled/concentrated to access and irrigate a lower pole stone. Catheter20 further comprises a thin, flexible tube 25 extending distally fromconnector 22 and a plurality of distal apertures 26 disposed at distalportion 28.

Catheter 20 is inserted through sheath 37 such that it extends distallyout of sheath distal opening 48 at sheath distal end 39. As statedabove, distal tube portion 28 pigtails in a preferred embodiment causingdistal apertures 26 to spread circularly. Catheter 20 comprises acatheter outer surface 29 and a catheter inner surface 30 as bestillustrated in FIG. 4. Catheter 20 defines a catheter lumen 31 that isin fluid communication with a catheter proximal opening 33 and distalapertures 26. A return passageway 51 is defined between catheter outersurface 29 and sheath inner surface 41. Fluid may be introduced intocatheter 20, directed through catheter lumen 31, and outputted at distalapertures 26 to contact the target body organ or body area. Asadditional fluid is continually directed to the body area throughcatheter lumen 31, the outputted fluid is recovered from the body areaby sheath 37. In particular, the outputted fluid enters sheath distalopening 48 and travels through sheath lumen 49 in a proximal direction.Specifically, returning fluid 57 travels in return passageway 51 betweencatheter outer surface 29 and sheath inner surface 41. Returning fluid57 does not disrupt entering fluid 59, which is shielded within catheter20.

Sheath 37 may comprise an access sheath similar to those used inconnection with dilators or obturators as illustrated in FIG. 3. In apreferred method for irrigating a body organ or cavity, an obturator 55is inserted through sheath 37 and is manipulated to move and positionsheath 37 to a desired location. For example, sheath tube 46 may beplaced to extend through a bladder 64 and a ureter 61 as illustrated inFIG. 1. Once sheath 37 is positioned such that sheath distal end 39 isadjacent a target body organ or cavity to be irrigated, obturator 55 maythen be removed thereby leaving sheath lumen 49 open for insertion ofcatheter 20. Catheter 20 is inserted through sheath 37 extendingdistally from sheath distal end 39.

An advantage of irrigation system 10 of the invention is an irrigant maybe introduced into catheter 20 at a high flow rate while maintaining alow pressure in the surrounding area to which the irrigant is directed.For example, an irrigant consisting of H₂O can be pressurized up to 200+cm while pressure is kept low in the surrounding area by sheath 37 whichrecovers the outputted irrigant. It will be appreciated that thishigh-flow low-pressure irrigation system may be used for a multitude ofmedical and surgical applications. For example, irrigation system 10 maybe employed for thermal applications such as renal cooling inlaparoscopic surgery. Renal hypothermia may be achieved withoutincurring the problems of systemic volume expansion or severehypothermia as commonly found in prior art techniques.

In another application of the invention, the irrigation system may beemployed for warming purposes during surgery. For example, irrigationsystem 10 may be used in connection with cryogenic ablation of a tumor.In this procedure, the target body organ, such as a kidney, is contactedby a cryogenic probe which freezes the contacted portion and surroundingportions of the body organ. Irrigation system 10 of the invention may beused to deliver warm, or at least warmer, fluid to the surrounding areaso as to limit the portions of the body organ being frozen. Irrigationsystem 10 thus facilitates more localized cryo-ablation to minimizedamages to healthy portions surrounding the target body organ. Theirrigation system of the invention could also be used to cool thekidney, thereby increasing the ablative capabilities of thecryo-ablation device.

In a further aspect of the invention, irrigation system 10 may beemployed for simply irrigating a body area. For example, irrigationsystem 10 may be used to flush out stone fragmentations 62 from aparticular area as illustrated in FIG. 5. Sheath 37 may be provided witha greater diameter, if necessary, to accommodate recovery of largerfragmentations. Other renal applications include alkaline irrigation fordissolution of uric acid stones, chemo-dissolution of cystine stones,irrigation with chemotherapy drugs after ureteroscopic tumor management,antibiotic irrigation of intra-abdominal abscess and severe infection(e.g., fungal and bacterial), and irrigation of thrombic agents.

It should be noted that the irrigation system of the invention may beadapted for use outside of the upper urinary tract. For example, system10 may be used in connection with continuous bladder irrigation andstomach lavage. In another example, system 10 may be used in centralnervous applications such as to clear a severe central nervous systeminfection. In yet another example, system 10 of the invention may beused for intra-uterine irrigation in treating endometriosis. Similarly,system 10 may be used in treating severe hypothermia in connection witha lavage using warmed irrigant to increase core body temperature.

From the foregoing description, it will be appreciated that the fluidused in the system of the invention may comprise a variety of differenttypes depending upon the application. The fluid may comprise a salinesolution set at certain temperatures for thermal applications. For otherapplications such as dissolution, the fluid may contain a chemicalsolution adapted to accomplish its specific objective.

FIG. 6 illustrates a high-flow low-pressure irrigation system 10 b inaccordance with a second embodiment of the invention. Irrigation system10 b comprises an access sheath 37 b and a flexible ureteral catheter 20b disposed inside the access sheath 37 b. Sheath 37 b is unique in thatin that it has a hub 66 at a sheath proximal end 38 b. Hub 66 forms aseal with catheter 20 b and includes an exit port or exit tube 68 fordirecting returning fluid 57 outward. In another embodiment of theinvention, an irrigation system 10 c may include a proximal Y-fittinghub 71 as illustrated in FIG. 7. Y-fitting hub 71 includes a first tube73 adapted for receiving a flexible catheter 20 c and a second tube 75adapted for directing the returning fluid outward. Both tubes 73 and 75are in fluid communication with each other and sheath lumen 49 c. Tube73 includes a proximal tube end 77 that forms a seal with flexiblecatheter 20 c to prevent the returning fluid from spilling.

In a preferred embodiment of system 10 c, the system is provided as aone-piece device where a sheath 37 c is secured to Y-fitting hub 71 at asheath proximal end 38 c and forms a seal around flexible catheter 20 cat a sheath distal end 39 c. It is understood that such a seal may beformed in a variety of ways. For example, sheath 37 c may be adhered orwelded to catheter 20 c at sheath distal end 39 c. Sheath apertures orports 79 are provided adjacent to sheath distal end 39 c to enable theoutputted fluid to return to sheath lumen 49 c.

In yet another embodiment of the invention, an irrigation system 10 d isprovided as one unit including a catheter 20 d and a sheath 37 d asillustrated in FIG. 8. Specifically, catheter 20 d is coupled to sheath37 d at sheath distal end 39 d. The cross-sectional area occupied bycatheter 20 d within sheath 37 d may be minimized to optimize the flowof the returning fluid. Similar to irrigation systems discussed above,system 10 d may be used for dissolving and recovering stone fragments.Within sheath 37 d, recovery of the returning fluid and stone fragmentscan be optimized by providing a larger gap between an inner surface 41 dof sheath 37 d and an outer surface 29 d of catheter 20 d. Outside ofsheath 37 d, a catheter distal portion may have a wall thickness that isgreater than the wall thickness of portion 82 disposed within sheath 37d so as to provide greater column strength and kink resistance.

It should be reminded that conventional catheters are designed tooperate as stand-alone devices. As such, conventional catheters need tohave bodies having sufficient column strength and kink resistance. Withirrigation system 10 d, however, catheter portion 82 within sheath 37 ddoes not need to meet the same performance requirements with regard tocolumn strength and kink resistance as the conventional cathetersbecause portion 82 is protected by sheath 37 d. As a result, the wallthickness of shielded portion 82 may be minimized thereby maximizing thecross-sectional area of return passageway 51 d.

FIGS. 9 and 10 illustrate that catheters 20 e and 20 f for use withseparate sheaths 37 e and 37 f, respectively, may still have thin walls.That is, whether a catheter is affixed to or separate from a sheath, thesheath provides the irrigation system with the necessary column strengthand kink resistance so as to enable the catheter to be thinned. In FIG.9, the wall of catheter 20 e has a thickness that expands outside ofsheath 37 e while in FIG. 10, the wall of catheter 20 f has a thicknessthat remains substantially the same within and outside of sheath 37 f.

FIGS. 11 and 12 illustrate another embodiment of a high-flowlow-pressure irrigation system 20 g comprising a multi-lumen conduit 84operating both as a sheath and a catheter. Conduit 84 comprises a commonwall 86 that forms a catheter lumen 31 g and a sheath lumen 49 g (seeFIG. 12). Catheter lumen 31 g provides a path for the inflow of fluid toa target body area and sheath lumen 49 g provides a path for the outflowor returning fluid from the target body area. The outflow of fluid ismaximized as catheter lumen 31 g can be minimized to occupy a smallercross-sectional area. Catheter lumen 31 g is sealed from sheath lumen 49g and is further defined by a catheter distal portion 28 g extendingdistally from conduit 84. Conduit 84 includes a distal opening 48 g influid communication with sheath lumen 49 g. Blunt obturators and otherinstrumentation may be inserted through the large sheath lumen 49 gdefined by conduit 84 for placement of irrigation system 20 g.

It will be appreciated that each embodiment of the invention ispreferably configured such that only the target body organ or area beingirrigated is exposed to the fluid. An input conduit and an outputconduit are provided for flushing and draining, respectively, of thefluid. In the above embodiments, the input conduit is a catheterdisposed adjacent to or inside the lumen of the output conduit, which isa sheath. It is anticipated, however, that the input conduit may be asheath flushing an irrigating fluid and the output conduit may be aninternal catheter draining the irrigating fluid. In such an embodiment,a pressure transducer may be used in the internal catheter so if or whenthe intravenal pressure reaches a set level, e.g., 30 cm H2O, the flowof the irrigating fluid could be automatically stopped. The lumen of theinput conduit is shielded from the lumen of the output conduit such thatthe flushing fluid and draining fluid do not disrupt each other's flow.The input conduit generally has a distal portion that projects out fromthe output conduit. The distal portion of the input conduit includesapertures for directing the fluid to the target body area. The outputtedfluid is recovered through a lumen having an opening or apertures at itsdistal end. It is foreseeable that the internal catheter and/or sheathis capable of sensing and recording pressure in the renal pelvis so asto adjust the flow of flushing and draining fluid in the irrigationsystem.

Many alterations and modifications may be made by those having ordinaryskill in the art without departing from the spirit and scope of theinvention. Therefore, it must be understood that the illustratedembodiments have been set forth only for the purposes of examples andthat they should not be taken as limiting the invention.

1. A high-flow low-pressure irrigation system (10) for directing a fluidto and recovering the fluid from an area within a body, comprising: asheath (37) defining a sheath lumen (49); and a flexible catheter (20)disposed in and through the sheath lumen (49), said flexible catheter(20) defining a catheter lumen (31) and comprising a plurality ofapertures (26) at a distal portion (28) that extends beyond the sheathlumen (49) and spreads in the body area, wherein the fluid is directedand outputted to the body area through the catheter lumen (31) and theapertures (26), and wherein the fluid outputted to the body area isreturned through the sheath lumen (49).
 2. The high-flow low-pressureirrigation system (10) of claim 1, wherein the distal portion (28)spreads in a pigtail configuration in the body area.
 3. The high-flowlow-pressure irrigation system (10) of claim 1, wherein the distalportion (28) spreads in a flared configuration providing a widedispersal of the fluid in the body area.
 4. The high-flow low-pressureirrigation system (10) of claim 1, wherein the distal portion (28) isconfigured to access and irrigate any part of a kidney.
 5. The high-flowlow-pressure irrigation system (10) of claim 1, wherein the distalportion (28) is configured to access and irrigate a lower pole stone ina kidney.
 6. The high-flow low-pressure irrigation system (10) of claim1, wherein the catheter lumen (31) is in fluid communication with acatheter proximal opening (33) and the apertures (26).
 7. The high-flowlow-pressure irrigation system (10) of claim 1, wherein the catheter(20) further comprises a catheter connector (22) at a catheter proximalend (24).
 8. The high-flow low-pressure irrigation system (10) of claim7, wherein the catheter (20) comprises a flexible tube (25) extendingdistally from the catheter proximal end (24), said flexible tube (25)including the apertures (26) at the distal portion (28).
 9. Thehigh-flow low-pressure irrigation system (10) of claim 1, wherein thecatheter (20) includes a catheter outer surface (29) and a catheterinner surface (30).
 10. The high-flow low-pressure irrigation system(10) of claim 9, wherein the sheath (37) comprises: a sheath funnel (42)disposed at a sheath proximal end (38) and having a sheath proximalopening (44); and a sheath tube (46) extending distally from the sheathfunnel (42) to a sheath distal end (39) where a sheath distal opening(48) is disposed.
 11. The high-flow low-pressure irrigation system (10)of claim 10, wherein the sheath (37) comprises a sheath outer surface(40) and a sheath inner surface (41).
 12. The high-flow low-pressureirrigation system (10) of claim 10, wherein the sheath (37) is shorterthan the catheter (20).
 13. The high-flow low-pressure irrigation system(10) of claim 11, wherein the catheter outer surface (29) and the sheathinner surface (41) define a return passageway (51).
 14. The high-flowlow-pressure irrigation system (10) of claim 10, further comprising anobturator (55) for moving and positioning the sheath (37) to a desiredlocation within the body.
 15. The high-flow low-pressure irrigationsystem (10) of claim 14, wherein the sheath (37) is positioned such thatthe sheath distal end (39) is adjacent to or inside a desired body areato be irrigated.
 16. The high-flow low-pressure irrigation system (10)of claim 1, wherein the distal portion (28) spreads the apertures (26)circularly.
 17. The high-flow low-pressure irrigation system (10) ofclaim 10, wherein the returning fluid (57) enters the sheath distalopening (48) and travels through the sheath lumen (49) in a proximaldirection.
 18. The high-flow low-pressure irrigation system (10) ofclaim 13, wherein the returning fluid (57) travels in the returnpassageway (51) and does not disrupt the entering fluid (59), which isshielded within the catheter lumen (31).
 19. The high-flow low-pressureirrigation system (10) of claim 1, wherein the fluid is introduced intothe catheter lumen (31) at a constant flow rate while maintaining a lowpressure in a surrounding area to which the fluid is directed.
 20. Thehigh-flow low-pressure irrigation system (10) of claim 1, wherein thefluid directed through the catheter lumen (31) can be pressurized up to200 cm.
 21. The high-flow low-pressure irrigation system (10) of claim19, wherein the pressure is kept low by the sheath (37) recovering thereturning fluid (57).
 22. The high-flow low-pressure irrigation system(10) of claim 1, wherein the system (10) is employed in minimallyinvasive surgery.
 23. The high-flow low-pressure irrigation system (10)of claim 19, wherein the fluid introduced into the catheter lumen (31)is warmer than fluid in the surrounding area.
 24. The high-flowlow-pressure irrigation system (10) of claim 19, wherein the fluidintroduced into the catheter lumen (31) is cooler than fluid in thesurrounding area.
 25. The high-flow low-pressure irrigation system (10)of claim 1, wherein the system (10) is employed to flush out stonefragmentations (62) from the body area.
 26. The high-flow low-pressureirrigation system (10) of claim 1, wherein the fluid comprises a salinesolution.
 27. The high-flow low-pressure irrigation system (10 b) ofclaim 1, wherein the sheath (37 b) comprises a hub (66) disposed at asheath proximal end (38 b) and having an exit port (68) for directingthe returning fluid (57) outward of the sheath (37 b).
 28. The high-flowlow-pressure irrigation system (10 b) of claim 27, wherein the hub (66)includes a Y-fitting component.
 29. The high-flow low-pressureirrigation system (10 c) of claim 10, wherein the sheath (37 c) forms aseal around the catheter (20 c) at the sheath distal end (39 c).
 30. Thehigh-flow low-pressure irrigation system (10 c) of claim 29, furthercomprising a plurality of sheath apertures (79) around the seal torecover and direct the returning fluid to the sheath lumen (49 c).
 31. Asystem for flushing and draining an area within a body, comprising: asheath defining a sheath lumen; and a catheter disposed in the sheathlumen and defining a catheter lumen, wherein the sheath operates toflush the body area with an irrigant, and wherein the catheter operatesto drain the irrigant from the body area.
 32. A high-flow low-pressureirrigation system (10 d) for directing a fluid to and recovering thefluid from an area within a body, comprising: a sheath (37 d) defining asheath lumen; and a flexible catheter (20 d) coupled to the sheath (37d), said catheter (20 d) having a first section disposed inside thesheath lumen and a second section disposed outside the sheath lumen,said catheter (20 d) defining a catheter lumen and comprising aplurality of apertures at a distal portion, wherein the fluid isdirected and outputted to the body area through the catheter lumen andthe apertures, and wherein the fluid outputted to the body area isreturned through the sheath lumen.
 33. The high-flow low-pressureirrigation system (10 d) of claim 32, wherein the first section of thecatheter (20 d) has a wall having a first thickness and the secondsection of the catheter (20 d) has a wall having a second thickness thatis thicker than the first wall thickness.
 34. The high-flow low-pressureirrigation system (10 d) of claim 32, wherein the sheath (37 d) forms aseal around the catheter (20 d) at one of a distal end of the firstsection and a proximal end of the second section.
 35. The high-flowlow-pressure irrigation system (10 d) of claim 32, wherein the distalportion of the catheter (20 d) curls in a pigtail configuration.
 36. Thehigh-flow low-pressure irrigation system (10 d) of claim 32, wherein thedistal portion of the catheter (20 d) spreads in a flared configuration.37. The high-flow low-pressure irrigation system (10 d) of claim 32,wherein the distal portion of the catheter (20 d) is configured toaccess and irrigate any part of a kidney.
 38. A high-flow low-pressureirrigation system (20 g) for directing a fluid to and recovering thefluid from an area within a body, comprising: a multi-lumen conduit (84)defining a first lumen (31 g) and a second lumen (49 g), saidmulti-lumen conduit (84) comprising a plurality of apertures at a distalportion (28 g), wherein the first lumen (31 g) is in fluid communicationwith the apertures, wherein the fluid is directed and outputted to thebody area through the first lumen (31 g) and the apertures, and whereinthe fluid outputted to the body area is returned through the secondlumen (49 g).
 39. The high-flow low-pressure irrigation system (20 g) ofclaim 38, wherein the distal portion (28 g) curls in a pigtailconfiguration.
 40. The high-flow low-pressure irrigation system (20 g)of claim 38, wherein the distal portion (28 g) spreads in a flaredconfiguration.
 41. The high-flow low-pressure irrigation system (20 g)of claim 38, wherein the distal portion (28 g) is configured to accessand irrigate any part of a kidney.
 42. The high-flow low-pressureirrigation system (20 g) of claim 38, wherein the cross-sectional areaof the first lumen (31 g) is less than the cross-sectional area of thesecond lumen (49 g).